Semiconductor workpiece proximity plating methods and apparatus

ABSTRACT

The present invention relates to methods and apparatus for plating a conductive material on a semiconductor substrate by rotating pad or blade type objects in close proximity to the substrate, thereby eliminating/reducing dishing and voids. This is achieved by providing pad or blade type objects mounted on cylindrical anodes or rollers and applying the conductive material to the substrate using the electrolyte solution disposed on or through the pads, or on the blades. In one embodiment of the invention, the pad or blade type objects are mounted on the cylindrical anodes and rotated about a first axis while the workpiece may be stationary or rotate about a second axis, and metal from the electrolyte solution is deposited on the workpiece when a potential difference is applied between the workpiece and the anode. In another embodiment of the present invention, the plating apparatus includes an anode plate spaced apart from the cathode workpiece. Upon application of power to the anode plate and the cathode workpiece, the electrolyte solution disposed in the plating apparatus is used to deposit the conductive material on the workpiece surface using cylindrical rollers having the pad or blade type objects.

CROSS-REFERENCE TO RELATED APPLICATION

This is a divisional application of U.S. Ser. No. 09/483,095, filed Jan.14, 2000.

FIELD OF THE INVENTION

The present invention relates to methods and apparatus for plating aconductive material on a semiconductor substrate. More particularly, thepresent invention is directed to “proximity plating” methods andapparatus for plating the conductive material on the semiconductorsubstrate. The substrate is plated with the conductive material as thepad and/or blade type objects are rotated in close proximity to thesubstrate.

BACKGROUND OF THE INVENTION

A conventional process step in the manufacturing of integrated circuitsand devices involves plating a conductive layer on a semiconductorsubstrate. Plating the substrate with the conductive material over aseed layer has important and broad application in the semiconductorindustry. Traditionally, aluminum and other metals are deposited as oneof many conductive layers that make up a semiconductor chip. However, inrecent times, there is great interest in copper deposition forinterconnects on semiconductor chips, because, compared to aluminum,copper reduces electrical resistance and allows semiconductor chips torun faster with less heat generation, resulting in a significant gain inchip capacity and efficiency.

Typically, the semiconductor substrate has been previously etched andcontains many holes and/or trenches on its surface. One goal of platingis to uniformly fill the holes and trenches with the conductivematerial.

However, as known in the art, conventional plating methods result in“dishing” or non-planar deposition during the plating process. In FIG.1A, a barrier layer 4 and a seed layer 6 is disposed upon a substrate 2,where a section of the substrate 2 includes a trench 12. After formingthe barrier layer 4 and the seed layer 6, a conductive layer 8 is platedon top of the seed layer 6. Because the trench 12 may be relativelylarge, a recess 10 is formed thereon and dishing results.

For small features with sub-micron size dimensions, existence of voidsin the deposited conductive layer is a common problem. In FIG. 1B, sucha void 14 is formed near the bottom of a narrow hole 16. It is wellknown that the existence of such voids in the deposited conductive layerresults in defective devices with poor performance. Accordingly, thepresent invention provides a more accurate, fast, cost effective, andreliable manner of applying the conductive material to the semiconductorsubstrate.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide methods andapparatus that deposit a conductive material on a substrate with the pador blade type objects rotating in a circular manner.

It is another object of the present invention to provide methods andapparatus that deposit a conductive material on a substrate whileeliminating/reducing dishing and voids.

It is yet another object of the present invention to provide methods andapparatus that deposit a conductive material on a substrate using novelpad-anode or blade-anode assemblies.

These and other objects of the present invention are obtained byproviding methods and apparatus for depositing a conductive materialfrom an electrolyte solution to the substrate. This is achieved byproviding pad or blade type objects mounted on cylindrical anodes orrollers and applying the conductive material to the substrate using theelectrolyte solution disposed on or through the pads or on the blades.

An apparatus that performs such plating includes anodes and a cathodeworkpiece that are in close proximity of each other. The pad or bladetype objects mounted on the cylindrical anodes or rollers rotate about afirst axis and the workpiece may be stationary or rotate about a secondaxis, and metal from the electrolyte solution is deposited on theworkpiece when a potential difference is applied between the workpieceand the anode.

Alternatively, the plating apparatus may include an anode plate spacedapart from the cathode workpiece. Upon application of power to the anodeplate and the cathode workpiece, the electrolyte solution disposed inthe plating apparatus is used to deposit the conductive material on theworkpiece surface using cylindrical rollers having the pad or blade typeobjects.

Further, in another embodiment, the plating apparatus may include ananode plate spaced apart from cylindrical cathodes having conductivepads or blades. Upon application of power to the anode plate and thecathodes and upon rotating the cathodes in a circular direction, theconductive pads or blades make electric contact to the workpiece surfacerendering it cathodic with respect to the anode plate, and metal from anelectrolyte solution is deposited on the same surface.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and advantages of the present invention willbecome apparent and more readily appreciated from the following detaileddescription of the presently preferred exemplary embodiments of theinvention taken in conjunction with the accompanying drawings, of which:

FIG. 1A illustrates a cross sectional view of a conductive layerdisposed on a substrate with “dishing” characteristics;

FIG. 1B illustrates a cross sectional view of a substrate having a holecontaining a void therein;

FIG. 2 illustrates a cross sectional view of a substrate having aconductive layer where dishing is eliminated/reduced;

FIG. 3 illustrates a cross sectional view of a “proximity plating”apparatus in accordance with the first preferred embodiment of thepresent invention;

FIGS. 4A-4B illustrate perspective views of pad-anode assemblies inaccordance with the preferred embodiment of the present invention;

FIGS. 5-6 illustrate cross sectional views of embodiments using anoderods in accordance with the preferred embodiment of the presentinvention;

FIG. 7 illustrates a cross sectional view of a “proximity plating”apparatus in accordance with the second preferred embodiment of thepresent invention; and

FIG. 8 illustrates a cross sectional view of a “proximity plating”apparatus in accordance with the third preferred embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention will now be describedwith reference to FIGS. 2-8. The inventors of the present inventionherein disclose methods and apparatus for “proximity plating” aconductive material on a semiconductor substrate. The present inventioncontemplates different embodiments to be used to plate/deposit aconductive material onto the substrate and into the contacts, vias,holes, trenches, and the like. While the present invention can be usedwith any conductive material, it is especially suited for use withcopper as the conductor and for use in the fabrication of VLSI and ULSIintegrated circuits having submicron size features. Furthermore,semiconductor workpieces such as a wafer, a flat panel, magnetic filmhead, or the like may be used in accordance with the present invention.

An example of a proximity plating method and apparatus is disclosed in aco-pending U.S. application Ser. No. 09/285,621, entitled “Method andApparatus For Plating and Polishing a Semiconductor Substrate”, commonlyowned by the assignee of the present invention, the contents of whichare expressly incorporated herein by reference. The present inventiondiscloses alternative embodiments.

One object of the present invention is to eliminate dishing. FIG. 2illustrates a cross sectional view of a substrate where dishing iseliminated/reduced as the conductive layer 8 is deposited onto thesubstrate 2. A relatively uniform flat conductive layer 8 can beobtained by plating the conductive material at a high mass transferrate, as described in more detail in the present invention. Anotherobject of the present invention is to eliminate voids in the platedmaterial. Eliminating/reducing dishing and eliminating voids are highlydesirable in order to manufacture a high quality integratedcircuit/device.

FIG. 3 illustrates a cross sectional view of a “proximity plating”apparatus in accordance with the first preferred embodiment of thepresent invention. FIG. 3 illustrates a nonconductive chamber 100 havingan electrolyte solution 110 disposed therein. The chamber 100 includesanode assemblies 120 a, 120 b, etc., having multiple strips of pads 130a, 130 b, etc., mounted, or machined onto the cylindrical anodes 140 a,140 b, etc. The cylindrical anodes 140 a, 140 b, etc., may be hollowcylinders formed from conductors such as carbon and titanium having adiameter between 10 to 30 mm.

As shown, the cylindrical anodes 140 a, 140 b, etc., are in partialcontact with the electrolyte solution 110. In other words, the top levelof the electrolyte solution 110 is below the surface of a workpiece 160(i.e., the top level of the electrolyte solution 110 does not makedirect contact with the workpiece surface when the cylindrical anodes140 a, 140 b, etc., are stationary). Alternatively, the electrolytesolution 110 may be making contact with the workpiece 160 surface.

During operation, a voltage is applied between the cylindrical anodes140 a, 140 b, etc., and a cathode workpiece 160. Electrical contact tothe cathode workpiece 160 is made via cathode contacts 184. When theanodes 140 a, 140 b, etc., and the pad strips (or pads) 130 a, 130 b,etc., are rotating about axis 150 in either a clockwise orcounterclockwise direction, and are spaced apart from the cathodeworkpiece 160 (the pad strips 130 a, 130 b, etc. do not make directcontact with the workpiece 160, or alternatively, make only slightcontact), the workpiece 160 is plated using the electrolyte solution110.

The anodes 140 a, 140 b, etc. and the pad strips 130 a, 130 b, etc.should preferably rotate at a rate such that the electrolyte solution110 is continuously “picked” by the anodes 140 a, 140 b, etc., andapplied/splashed onto the workpiece 160. They may all rotate in the sameclockwise or counterclockwise direction or alternatively, some mayrotate in one direction (i.e., clockwise) while others may rotate in theopposite direction (i.e., counterclockwise). Further, during operation,one, two, three, . . . , or all anodes 140 a, 140 b, etc., may beactivated concurrently and voltages may be applied to all or only aselected number of them. Anode current densities for different anodes140 a, 140 b, etc., may vary, and this can be used to control theuniformity of the deposited material across the workpiece 160. Inaddition, the length of the anodes 140 a, 140 b, etc., may all be thesame or they may be different.

When the gaps between the pads 130 a, 130 b, etc., and the workpiece 160are about 0-5 mm and contains a meniscus of electrolyte solution 110, avery high mass transport results, thereby depositing high quality metalfilms onto the workpiece 160. Moreover, when electric power is appliedto the cylindrical anodes 140 a, 140 b, etc., and the cathode workpiece160, a closed electrical circuit is formed through the anode assemblies120 a, 120 b, etc., the applied/splashed electrolyte solution 110 in thegaps, and the workpiece 160. This is described in more detail below.Moreover, depending on the type, shape, and structure of the pads 130 a,130 b, etc., the gaps may be greater than 5 mm.

The workpiece head assembly 180 may include a nonconductive, preferablycircular chuck 182 with a cavity that is preferably a few millimetersdeep at its center and which cavity may contain a resting pad (notshown). The workpiece 160 is loaded into the cavity, backside first,against the resting pad using a conventional type of transport or vacuummechanism to ensure that the workpiece 160 is stationary with respect tothe workpiece head assembly 180 while in use. A nonconductive retainingring (not shown) such as an O-ring or other rubber type of seal at theperiphery of the workpiece head assembly 180 and the cathode contacts184 each push against the edge of the workpiece 160 and hold it inplace. The entire back side of the workpiece 160 which pushes againstthe chuck 182 that is under the retaining ring is thus protected fromany and all solutions, including electrolyte. Other conventionalworkpiece head assemblies can be used in accordance with the presentinvention.

As shown, the workpiece head assembly 180 faces toward the anodeassemblies 120 a, 120 b, etc. The head assembly 180 may be stationary orrotate around axis 190 using a conventional motorized spindle (notshown). The head assembly 180 may also be adapted to move up and downand/or side to side in the direction of arrow 192 so that the workpiece160 may be plated more effectively.

Instead of using the cathode contacts 184 described above, the electricpotential can be applied to the workpiece 160 using a ring conductor.Further, other methods of applying the electric potential to theworkpiece may be used in accordance with the present invention. Forexample, a liquid conductor or an inflatable tube coated with aconductive material may be used in the present invention. An example ofusing the liquid conductor or the conductive tube to provide thenecessary electric potential is disclosed in the co-pending U.S.application Ser. No. 09/283,024, entitled “Method And Apparatus ForForming an Electric Contact With a Semiconductor Substrate”, commonlyowned by the assignee of the present invention, the contents of whichare expressly incorporated herein by reference. What is important tonote from the previous examples is that any method for providing anelectric potential between the anode or anodes and the cathode workpiececan be used in the present invention.

FIG. 4A illustrates a perspective view of a first pad-anode assembly inaccordance with the present invention. An anode assembly 122 (120 a, 120b, etc. in FIG. 3) includes a unique pad-anode arrangement for platingthe workpiece 160. Multiple strips of pad 132 (130 a, 130 b, etc. inFIG. 3) are attached, glued, or machined onto a cylindrical anode 142(140 a, 140 b, etc. in FIG. 3) such that the pads 132 protrude from theouter surface of the anode 142. In this arrangement, the pads 132 areformed on the anode 142 in a circular manner such that the pads 132 wraparound the anode 142. The cylindrical anode 142 is further connected toa shaft 192 for rotating about axis 150.

FIG. 4B illustrate a perspective view of a second pad-anode assembly inaccordance with the preferred embodiment of the present invention.Again, the anode assembly 124 (120 a, 120 b, etc. in FIG. 3) includes aunique pad-anode arrangement for plating the workpiece 160. Similar toFIG. 4A, multiple strips of pad 134 (130 a, 130 b, etc. in FIG. 3) areattached, glued, or machined onto a cylindrical anode 144 (140 a, 140 b,etc. in FIG. 3) such that the pads 134 protrude from the outer surfaceof the anode 144. However, in this arrangement, the pads 134 are formedon the anode 144 in a manner such that the pads 134 run along thelongitudinal side of the cylindrical anode 144 in a substantiallystraight manner. This is illustrated in FIG. 4B. The cylindrical anode144 is further connected to a shaft 194 for rotating about axis 150.

It should be appreciated that many other designs of pad strips can alsobe used effectively in the present invention. What is important is thatthese strips cause rigorous stirring of the electrolyte at the workpiecesurface. The pad strips described thus far in FIGS. 3, 4A, and 4B arerelatively wide (2 to 20 mm). In other embodiments, narrow strips (1 to2 mm) that are shaped like blades can be used in the present invention.These blades are of a type similar to windshield wiper blades used inautomobiles and are made preferably from polymeric materials that arecompatible with the plating solution used in the invention. The padstrips may be made of a porous or non-porous polymeric material with orwithout abrasive particles contained therein. Both the pad strips andblades can be rigid or flexible. What is important is that the padstrips/blades material is stable and can be employed in conjunction withvarious plating solutions that can be used in this invention.

In another embodiment of the present invention, the pad strips or blades130 a, 130 b, etc., in FIG. 3 may be made of a conductive material. Inthis case, it should be assured that the pad strips or blades 130 a, 130b, etc., do not touch the workpiece 160 surface during the platingoperation, as described in more detail later herein.

FIGS. 5-6 illustrate cross sectional views of embodiments using anoderods in accordance with the preferred embodiment of the presentinvention. In these embodiments, rather than having one largecylindrical anode for each anode assembly as shown in FIG. 3, multipleanode rods are enclosed in cylindrical anode assemblies. For example,FIG. 5 illustrates an anode assembly 300 having multiple anode rods 310a, 310 b, etc., extending from one end of the assembly 300 to the otherend within the cylindrical space contained by the wall 300 a.Preferably, the anode rods are between 1 mm to 3 mm in diameter.Although the anode rods 310 a, 310 b, etc., are schematically shown asnot in contact with each other, the anode rods 310 a, 310 b, etc., maybe in contact with each other in other embodiments. Furthermore, anodepellets of various shapes and sizes may be substituted for anode rods inthe cylindrical cavity within the walls 300 a or a combination of anoderods and pellets may be used.

The anode assemblies of FIGS. 5 and 6 should preferably includepores/holes 300 b, as shown herein. The plating solution can enter thecylindrical cavity through the pores/holes 300 b, thereby forming anelectrical and physical contact between the plating solution and theanode rods/pellets.

The anode assembly 300 also includes pads 320 (130 a, 130 b, etc. inFIG. 3) as described earlier. A shaft 330 extends through the center ofthe anode assembly 300 such that the anode assembly 300 may be rotatedin a circular motion (either clockwise or counterclockwise). Thematerial 340 surrounding the rods/pellets 310 a, 310 b, etc, and theshaft 330 is preferably made from an insulating polymeric material. Theanode rods/pellets 310 a, 310 b, etc., are preferably made from the samematerial that is deposited on the workpiece. For example, for Cudeposition, rods/pellets 310 a, 310 b, etc., should be preferably madefrom Cu. The rods/pellets 310 a, 310 b, etc., may be replacedoccasionally as they are in constant use.

FIG. 6 illustrates an anode assembly 350 similar to that of FIG. 5except blades 360 are used instead of pads 320.

FIG. 7 illustrates a cross sectional view of another embodiment of thepresent invention where a separate anode plate is used instead of thecylindrical anodes. A chamber 400 includes one or more cylindricalrollers 410 a, 410 b, etc., having pad type objects 420 a, 420 b, etc.,attached/mounted thereon. The rollers 410 a, 410 b, etc., are preferablymade from polymeric materials or metals such as Ti that are chemicallyand mechanically stable in an electrolyte solution 440. The pad typeobjects 420 a, 420 b, etc., are attached, mounted, etc. on the rollers410 a, 410 b, etc., in a manner similar to that described with referenceto FIG. 3.

The chamber 400 includes an anode plate 460 on the bottom of the chamber400. Any known method for attaching the anode plate 460 to the bottom ofthe chamber 400 may be used. In the alternative, the anode plate 460 maybe positioned at any other location in the chamber 400 so long as itmakes physical contact with the electrolyte solution 440. Theelectrolyte solution 440 in the chamber 400 also makes contact with thepads 420 a, 420 b, etc. The electrolyte solution 440 can be originallyfed into the chamber 400 via a reservoir (not shown) through anin-channel (not shown).

Upon application of power between the workpiece 160 via, for example,contacts 184 and the anode plate 460, and upon rotating one or morerollers 410 a, 410 b, etc. about axis 450 in either a clockwise orcounterclockwise direction, the electrolyte solution 440 is continuouslysplashed/applied to the workpiece 160 via pads 420 a, 420 b, etc. Shafts470 a, 470 b, etc., are used to rotate the rollers 410 a, 410 b, etc,respectively. Thus, metal is plated out of the electrolyte solution 440onto the workpiece 160 surface. As disclosed earlier herein, rollerswith blade type objects instead of pads can be used.

In another embodiment of the present invention, the pad/blade 420 a, 420b, etc. material in FIG. 7 may be constructed/made from a highlyconductive fabric or polymeric material such as polyanilines. In thiscase, the electric contact 184 to the workpiece 160 is not needed.Instead, an electric contact to the conductive pads/blades 420 a, 420 b,etc., is provided (not shown). Upon application of power between theanode plate 460 and conductive pads/blades 420 a, 420 b, etc., and uponrotating the rollers 410 a, 410 b, etc., in a manner such that thepads/blades 420 a, 420 b, etc., make contact with the workpiece 160surface, the electrolyte solution 440 is continuously applied to theworkpiece 160, and metal from the electrolyte solution 440 is platedonto the workpiece 160 surface. It should be noted that in this case,cathodic voltage is applied to the workpiece 160 surface using theconductive pads/blades 420 a, 420 b, etc., as they make contact with theworkpiece 160. Metal from the electrolyte solution 440 is plated on theworkpiece 160 surface rather than on the conductive pads/blades 420 a,420 b, etc., because plating efficiency is much higher on the workpiece160 surface than on the conductive pads/blades 420 a, 420 b, etc.

FIG. 8 illustrates yet an additional embodiment of the presentinvention. While operating the anode assemblies in FIG. 8, theelectrolyte solution can be introduced to the pads or blades from aninlet channel (not shown) located inside or in proximity to the anodes.A chamber 600 includes anode assemblies 610 a, 610 b, etc., having padtype objects 620 a, 620 b, etc., attached/mounted on the cylindricalanodes 630 a, 630 b, etc. Shafts 640 a, 640 b, etc., are used to rotatethe anode assemblies 610 a, 610 b, etc., about axis 650. In thisembodiment, unlike the previous embodiments, an electrolyte solution isnot disposed in the chamber 600. The electrolyte solution is flowedthrough the anode assemblies 610 a, 610 b, etc., via passageways andholes within the outer periphery of the anodes 630 a, 630 b, etc., whichprovide paths for the solution to be fed to the gaps between the anodes630 a, 630 b, etc., and the cathode workpiece 160. Alternatively, theelectrolyte solution can be dispensed directly onto the anode assemblies610 a, 610 b, etc., through another channel (not shown). The electrolytesolution that drops to the bottom of the chamber 600 is flowed out ofthe chamber 600 via one or more outlet passageways 690. Other means ofremoving the electrolyte solution from the chamber 600 may be used inaccordance with the present invention.

The attractive feature of the design of FIG. 8 is that the apparatus canbe operating in a vertical geometry (i.e., apparatus in FIG. 8 rotatedby 90 degrees). In other embodiments, a configuration where the anodeassemblies 610 a, 610 b, etc., are positioned over of the cathodeworkpiece, rather than underneath, can be implemented.

Referring back to the embodiment in FIGS. 7 and 8, the rollers 410 a,410 b, etc., having the pad strips 420 a, 420 b, etc., and the anodeassemblies 610 a, 610 b, etc., should preferably rotate at a rate suchthat the electrolyte solution is continuously applied/splashed onto theworkpiece. The rollers 410 a, 410 b, etc., or the anode assemblies 610a, 610 b, etc., may all rotate in the same clockwise or counterclockwisedirection or alternatively, some may rotate in one direction (i.e.,clockwise) while others may rotate in the opposite direction (i.e.,counterclockwise). Further, during operation, one, two, three, . . . ,or all rollers 410 a, 410 b, etc., or anode assemblies 610 a, 610 b,etc., may be activated concurrently and/or voltages may be applied toall or only a selected number of them (only anode assemblies 610 a, 610b, etc.). In addition, the length of the rollers 410 a, 410 b, etc., andthe anode assemblies 610 a, 610 b, etc., may all be the same or they maybe different.

In all embodiments described herein, the hardness of the pad or bladetype objects is related to the relative speed of rotation of the pads orblades with respect to the workpiece.

Although both DC and pulsed power supplies can be used to apply power tothe anode(s) and the workpiece, the present invention may reduce theneed for pulse generating power supplies because the mechanical pulsingthat is generated from the movement of the pads or blades relative tothe face of the workpiece creates sufficient pulsing. This mechanicalpulsing is created as a result of the workpiece being in proximity withthe pads or blades as it is moved in relation to the workpiece. Thebenefit of the mechanical pulsing is that it improves grain size,filling efficiency of the contact holes, vias, and trenches, and copperfilm integrity without the need for power supplies with pulsingcapabilities.

In additional to the mechanical pulsing, the anode assemblies disclosedherein can provide electrical pulsing. If the pad and/or blade materialsare insulating, then the plating current density decreases as thecylindrical anode is rotating when the pad and/or blades are in theirclosest distance to the workpiece surface. On the other hand, when thepad/blade is not in their closest distance to the workpiece surface(i.e., the gaps in between each pad/blade) as the cylindrical anode isrotated, then the current density increases. Such pulsing is found to bebeneficial for forming a high quality material on the workpiece surface.

Although deposition of a conductive material has so far been describedhereinabove, those skilled in the art can use the teachings herein foretching and electroetching processes. For example, if the voltageapplied between the workpiece and the anode(s) is such that theworkpiece is more negative than the anode(s), then plating on theworkpiece surface occurs. If the voltage is zero, then chemical etchingof the conductive material on the workpiece surface occurs. If thepolarity voltage is reversed, then electroetching of the conductivematerial from the workpiece surface can be initiated. Alternately, theapparatus disclosed herein can be used for electroless deposition ofmaterials such as Cu, Ni, Ni—P, Co, etc. In this case, an electrolessdeposition solution is used rather than the electrodepositionelectrolyte solution.

Although the embodiments shown thus far illustrate one workpiece, it isunderstood that more than one workpiece head assembly could be used withthe present invention. Furthermore, each chamber described above mayinclude various numbers of anode/roller assemblies so long as they caneffectively plate a conductive layer on a workpiece surface.

In the previous descriptions, numerous specific details are set forth,such as specific materials, structures, chemicals, processes, etc., toprovide a thorough understanding of the present invention. However, asone having ordinary skill in the art would recognize, the presentinvention can be practiced without resorting to the details specificallyset forth.

Although only the above embodiments have been described in detail above,those skilled in the art will readily appreciate that many modificationsof the exemplary embodiment are possible without materially departingfrom the novel teachings and advantages of this invention.

I claim:
 1. An apparatus for depositing a conductive material on asurface of a workpiece, comprising: a workpiece head assembly adapted tosupport the workpiece; a chamber having: a plurality of rollers, whereineach roller is adapted to rotate in a circular direction and includesone or more pad or blade strips attached to an outer surface of theroller, wherein the chamber is adapted to hold an electrolyte solutionincluding the conductive material, the electrolyte solution adapted tobe applied to the surface of the workpiece upon rotating the pluralityof rollers; and an anode plate positioned in the chamber such that theelectrolyte solution makes contact with the anode plate.
 2. Theapparatus according to claim 1, wherein the anode plate is positioned ona bottom wall of the chamber.
 3. The apparatus according to claim 1,wherein the anode plate is positioned on a side wall of the chamber. 4.The apparatus according to claim 1, wherein the one or more pad or bladestrips are wrapped around the outer surface of the roller.
 5. Theapparatus according to claim 1, wherein the one or more pad or bladestrips are attached to the outer surface of the roller along alongitudinal side of the roller.
 6. The apparatus according to claim 1,wherein the workpiece head assembly is further adapted to move up anddown and side to side.
 7. The apparatus according to claim 1, whereinthe workpiece head assembly is further adapted to rotate in a clockwiseor counterclockwise direction.
 8. The apparatus according to claim 1,wherein the one or more pad strips include widths that are 2-20 mm. 9.The apparatus according to claim 1, wherein the one or more blade stripsinclude widths that are 1-2 mm.
 10. The apparatus according to claim 1,wherein the one or more pad strips comprise one of porous, non-porous,conductive, and non-conductive material.
 11. The apparatus according toclaim 1, wherein the one or more pad strips further include abrasiveparticles.